Mexico map for Nuvi 500

Well, apparently the 500 comes with a basic map of Mexico that will show major roads but not a very detailed map that shows the smaller roads and best of all,,,, dirt roads{please correct me if I'm wrong on that}. I looked at Garmin's site and they offer a N.American map that includes detailed Canadian maps but it appears, the same basic Mexican map that the 500 aready has so all I would be gaining would be Canada.

Garmin offers a stand alone Mexico map once again, it appears that even this map is just like the basic Mexican map already included. Seriously, it looks like Garmin has a crapload of very detailed maps for places all over the world but from what I could tell,,,,, they don't have a detailed map of Mexico. Am I having a brain cramp here????

Also, while looking for the detailed Mexican maps I read several references that state that one can not use the lifetime update maps as it will confuse the unit {basically, Garmin sorta loaded two maps in the 500, the City Nav and the Topo 100K} and you will lose the ability to have the Topo. Anyone know if Garmin has addressed this issue? You would think they wouldn't offer the lifetime updates for the 500 if they knew this would happen????